Unchecked runtime.lastError: Could not establish connection. Receiving end does not exist.

[Morten Overgaard]

Situation:

Inject.js is injected into the page's MAIN world using chrome.scripting.executeScript from background.js

Everything works as expected except when trying to send a message from inject.js  back to extension.

The message actually hits the target but always followed by the error

Unchecked runtime.lastError: Could not establish connection. Receiving end does not exist.

// inject.js

chrome.runtime.sendMessage("<extensionId>","Test", (resp => {

console.log(resp);

res("OK");

}));

The same happens when trying the below - any idea why ??

 chrome.runtime.connect(<extensionid>,{});

br Morten

[Stefan vd]

Hi br,

Do you have this issue also with this sample code (manifest v3)? That with this background listener:

background.js
// Example of a simple user data object
const user = {username: 'demo-user'};
chrome.runtime.onMessage.addListener((message, sender, sendResponse) => {
// 2. A page requested user data, respond with a copy of `user`
if (message === 'get-user-data') {
sendResponse(user);
}
});

inject.js
// 1. Send the background a message requesting the user's data
chrome.runtime.sendMessage('get-user-data', (response) => {
  // 3. Got an asynchronous response with the data from the background
  console.log('received user data', response);
  initializeUI(response);
});

Source: https://developer.chrome.com/docs/extensions/reference/runtime/#example-content-msg

Thanks,

Stefan vd

[Morten Overgaard]

I have no problems when using runtime.sendMessage from  a "normal" content script - everything is all god.

// background.js

...

let resp = chrome.scripting.executeScript({

target: { tabId: t.id},

files : ["./extension/src/inject.js"],

world: "MAIN",

}); 

Its when inject.js gets injected into the page's main world context the error occurs

calling runtime.sendMessage from inside inject.js fails with the error.

makes sense ? 

[wOxxOm]

To receive messages from the page you need to use a different event: chrome.runtime.onMessageExternal and declare externally_connectable in manifest.json, see the documentation: https://developer.chrome.com/extensions/messaging#external-webpage

[wOxxOm]

BTW if you only send a single message, you can simply return a Promise as the last evaluated expression in the script instead of messaging, which will be transferred to the result of executeScript.